1. Field of the Invention
The invention relates to an enclosure for a power converter intended for a rail vehicle traction system.
2. Description of the Prior Art
The performance of power electronic modules is known to be limited by the temperature reached by the power electronic components in operation due to heating caused by the dissipation of power by the Joule effect. The performance of a silicon chip is strongly degraded beyond 150xc2x0 C., for example. Also, the reliability of power electronic components is strongly degraded above 100xc2x0 C.
Because of this, it is very important to provide a cooling system to evacuate the heat generated, in order to maintain an optimum operating temperature in the components and thereby to be in a position to increase the power that can be used. In particular, with some components, such as IGBT, the maximum permitted current is a function of the quantity of heat that the device is capable of evacuating.
The solution most usually adopted on rail vehicles for cooling power modules used in the converters is to apply an aluminum heatsink with cooling fins to the base of each of the power modules, the combination of the modules and their heatsinks being disposed in an enclosure situated under the vehicle and open at the sides to enable a flow of air, especially when the vehicle is moving.
However, this solution has the drawback that the cooling of the power modules is not very effective, in particular when the vehicle is stationary and no flow of air is traveling over the heatsinks. This lack of cooling leads to the use of a greater number of power components, in order to reduce the current in each power component and therefore to reduce the heating thereof, which has the drawback of increasing the cost, overall size and weight of the power converters.
This problem can be partly solved by using fans to create a permanent flow of air over the heatsinks. However, fans have the drawback of generating a great deal of noise, of being somewhat unreliable, and of having a short service life in the rail environment.
The object of the present invention is therefore to propose an enclosure for power electronic modules that ensures excellent and highly reliable cooling of the power components within a small overall size, thereby reducing the number of power electronic modules needed to implement an inverter installation in a rail vehicle traction system.
To this end, the invention provides a power converter enclosure, intended in particular to equip a rail vehicle traction system including power electronic modules comprising one or more power semiconductor components mounted on a substrate, which enclosure includes a base including a bottom panel with double walls having an inside wall on the side toward the interior of the enclosure in contact with at least one substrate supporting a power component, the bottom panel being extended by at least two lateral panels with double walls whose outside walls are cooled by cooling fins, and in which enclosure the two walls of the bottom panel delimit a hollow volume partly filled with a cooling liquid and containing a thermally conductive permeable material providing a thermal bridge between the two walls.
Particular embodiments of the enclosure according to the invention can have one or more of the following features, in isolation or in any technically feasible combination:
the thermally conductive permeable material is a porous material such as copper foam injected into said hollow volume defined by the two walls;
the thermally conductive permeable material comprises a stack of copper or aluminum grids between the two walls;
the lateral panels have an accordion-shape outside wall defining said cooling fins;
the lateral panels have a plane outside wall to which said cooling fins are attached;
one or more passive components are in contact with the inside wall of the double-wall lateral panels;
a cover of complementary shape to the base closes said enclosure;
the bottom panel of the base has a plane outside wall;
the bottom panel of the base has an outside wall cooled by cooling fins; and
the power components are IGBT.
The aims, aspects and advantages of the present invention are explained in the following description of embodiments of the invention, which is given by way of nonlimiting example and with reference to the accompanying drawings.